Difiuprednate (6.alpha.,9.alpha.-difluoroprednisolone 17-butyrate 21-acetate) is an antiinflammatory steroid which is known to show superior antiinflammatory action by percutaneous administration (U.S. Pat. Nos. 3,780,177, 3,784,692). In addition, difluprednate is reported to show superior antiinflammatory action and antiallergic action by percutaneous administration and subcutaneous administration (Pharmacometrics, 29 (3), 343-353 (1985), Pharmacometrics, 29 (3), 355-362 (1985)). Therefore, difluprednate is mainly used as a therapeutic drug in the preparation form of ointment, cream and the like for skin disorders.
On the other hand, when difluprednate is administered locally to an eye, nose, ear or the like, a liquid dosage form, such as an eye drop, a nasal drop, an ear drop and the like, is desirable. However, inasmuch as difluprednate has extremely low solubility in water, it is difficult to prepare a stable eye drop, nasal drop, ear drop or the like, containing difluprednate in a concentration effective for treatment, and a dosage form of an aqueous suspension has been proposed for the administration to the local sites as mentioned above (U.S. Pat. No. 5,556,848).
When, for example, an aqueous suspension of difluprednate is used as an eye drop, however, common problems associated with aqueous ophthalmic suspensions, namely, difficulty in sustaining uniform drug distribution upon instillation, uncomfortable feeling caused by solid entering into the eye and inability to completely eliminate foreign sensation, have been pointed out. In addition, since difluprednate is an antiinflammatory steroid, it is on the one hand sufficiently effective for the treatment of inflammatory diseases, allergic diseases and the like, but on the other hand associated with side effects. Thus, there is a need for the development of a dosage form permitting quick and uniform transfer of an effective amount of difluprednate and causing less side effects, in view of a case where a part (e.g., inner ocular area) distant from the instillation site (e.g., outer ocular area) has an inflammation.